Design of plain masonry basement walls

Abstract

Basements for dwellings and small buildings have been the subject of great interest in recent years because they represent a big gain in space within the same footprint. There are many other factors in favour of basements including the inherently good energy efficiency and the fact that many sites require fairly deep excavation even if a basement is not Included. The demand for authoritative guidance has resulted in the production of an Approved Document but because of limitations in the design methods and assessment of loads it was not possible to include plain masonry walls. It is clear that plain masonry walls should be appropriate in many situations but the absence of a sustainable design method is inhibiting their use. An empirical design method for very specific conditions based on German practice is included in Eurocode 6 2 but this is of limited applicability to UK conditions. The research programme described in this paper has reviewed all the design information available and proposes a design basis for plain masonry basement walls. The investigation has found that by refining the underlying design assumptions which form the basis of EC 6 a 20% Improvement in the performance of unreinforced masonry can be achieved. A detailed method of design is presented for typical UK dwelling construction. It is unlikely that any further gain in design economy for plain masonry walls can be achieved by further refinement of the design assumptions for the masonry. There would be significant gains to be made by rationalising the loading assumptions for shallow basement walls but further research is required before this can be justified.